[R] Chi-squared test adjusted for multiple comparisons? Harbe'stest?

[Murray Cooper]

Categorical data analysis is definitely the way you want to go.
Which test you use depends on how you are going to use the results.

For "quick and dirty" I would suggest using Fisher's exact test on all
2x2 submatricies of counts. In this case, with 4 treatments you have
6 possible 2x2 submatricies. See "fishers.test" function.

Another possibility would be a log-linear model, to model Ln(p/q).

Murray M Cooper, Ph.D.
Richland Statistics
9800 N 24th St
Richland, MI, USA 49083
Mail: richstat at earthlink.net

----- Original Message ----- 
From: "Laura Lucia Prieto Godino" <llp23 at cam.ac.uk>
To: <r-help at r-project.org>
Sent: Thursday, February 05, 2009 7:06 AM
Subject: [R] Chi-squared test adjusted for multiple comparisons? 
Harbe'stest?


> Hi!
>
> I have some data that looks like this
> up down percentaje
> uew_21 20 14 58.82
> uew_20_5 27 40 40.29
> uew_20 8 13 38.09
> uew_19_5 17 42 28.81
>
>
>
> So I have 4 experimental conditions and I am counting number of
> animals in the up and down compartment and the calculating the
> percentage, I want to know which one of the conditions is different
> from each other. If the data wouldn't be percentage I would runt a
> kruskal-wallis test to check for general differences and then when
> significan a post-hoc test, comparing differents pairs with Man-
> Whitney (wilcoxon function in R) with a bonferroni correction for
> multiple comparisons. But as the data are in the percentaje form, I
> know I need to analize them with either a chi squared or a g-test, but
> I have no idea if I can do such a test with many comparissons or how
> to do it in R, as well I have seen a paper in which they do something
> similar and they are using a Harber's chi squared test. Does anybody
> know how to do that in R?
>
> Thank you  very much for your help, and thanks to the jim and chuck
> for answering my previous statistical question!
>
> Lucia
>
> [[alternative HTML version deleted]]
>
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